Hydraulic lift



Au 7, 1945. R C N N 2,381,664

' HYDRAULIC LIFT Filed Jan. 15, 1944 s Sheets-Sheet 1 K I v I Inz'entorfig. 2. J 15 4A ,5 a4

' I C. V/c T02 HH/VSEA/ B) 1 '1 WWW MIZZW Aug. 7, 1945.

C. V. HANSEN HYDRAULIC LIFT Filed Jan. 15, 1944 3 Sheets-Sheet 2 r m n ev 6 Me 702 HU/VSE/VI A 7,1945 0. v.. HANSEN Q 2,381,664

HYDRAULIC LIFT Filed Jan. 15, 1944 3 Sheets-Sheet 3 I n uentar C 7'02HHNSEA/ Patented Aug. 7, 1945 IE OFFIQ Claims.

his invention relates to hydraulic lifts embodying a lift frame mountedon the vertically movable pistons of a plurality of similar hydraulicjacks.

The primary object of the present invention is to provide means forforcing the power transmission liquid into the cylinders of thehydraulic jacks so that exactly the same pressure will be applied to thepistons of all of the jacks and said pistons of the hydraulic jacks willbe caused to move exactly the same distances.

In carrying out the above object, I provide a hydraulic lift including aplurality of similar pumps for forcing the power transmission liquidinto the jack cylinders, a single common actuator being provided for thepistons of all of the pump cylinders, and means being provided toautomatically keep the pump cylinders filled with power transmissionliquid to compensate for any power transmission liquid lost from any ofthe jack cylinders by reason of leakage or the like.

A further more specific-object of the present invention is to provide ahydraulic lift of the above character involving a minimum number ofmovable parts that are durable and compactly arranged so as to beeffectively protected against access of foreign matter thereto that maycause undue wear thereof.

In a preferred embodiment of the invention,

' "the pistons of the pumps are preferably carried by a single operatingpiston movable in a master cylinder and reciprocable by fluid underpressure.

Other objects and features of the invention will become apparent fromthe following description when considered in connection with theaccompanying drawings, and the invention consists in the novel form,combination andarrangement of parts hereinafter more fully described,shown in the drawings, and claimed.

in the drawings, wherein like reference characters indicatecorresponding parts throughout the several views: I

Figure l is a top plan viewof an embodiment of the invention suitablefor use as a power lift for molding machines.

Figure 2 is an elevational view'thereof.

Figure. 3 is a longitudinal vertical section taken on line 33 of Figure1, and partly broken away.

Figure, 4 isa vertical transverse sectiontaken on line 4-4 of Figure 2.

Referring in detail to the drawings, the illusrectangular base plate 5having a plurality of similar hydraulic jacks mounted thereon, one ateach corner of the base plate. Each jack 5 includes a vertical cylinderl suitably secured upon the base plate 5, and a vertically movablepiston 8 operable in and projecting upwardly from the associatedcylinder '6. A lift frame is mounted upon the jacks 6, said frameincluding a pair of spaced parallel horizontal side frame bars 9 boltedat their ends upon theupper ends of the jack pistons 3 at thecorresponding sides of the base plate, as at it), said frame bars 9being rigidly connected near opposite ends thereof by means oftransverse frame members ll of substantially U-shape. The connectingmembers it of the frame are afixed at their ends to the under sides ofthe frame bars 9 inwardly of the jacks, and they extend downwardly andthen transversely from one frame bar 9 to the other at a point,considerably below the frame bars Q.

Mounted upon the base plate 5 intermediate the ends thereof is acylinder block if having a large master cylinder it at the top portionthereof and formed in its lower portion with a plurality of smaller pumpcylinders it corresponding in number to the number of hydraulic jacks b.Each pump cylinder M is connected at the bottom with one of the jackcylinders at the bottom of the latter by means of a passage l5,

whereby the power transmission fluid may be forced from a pump cylinderinto each jack cylinder. A plurality of pump pistons it are suitablycarried by and depend from a master piston ii operating in mastercylinder 13, said pump pistons it corresponding in number to and workingin the pump cylinders I l. Thus, the master piston l'i constitutes asingle common actuator for all of the pump pistons. A table top orplatform it is placed and secured upon the top of the cylinder block ifand extends beyond opposite sides of the latter so as to completely fillthe space between the frame bars ii. The table or platform it thus formsa head for closing the upper end of the master cylinder l3,said-cylinder it? being provided with combi ed inlet and outlet ports asand it, respectively, near the top and bottom thereof. A pipe 2 l whichextends from any suitable source of supply of fluid under pressure, is

trated embodiment of the invention includes a provided with branches 22and 2% respectively communicating with the ports is and it, and associated with these branches is a control valve 24 of any well known orpreferred construction by means of which fluid under pressure may beadmitted to either port I 9 or 20 whilesimultaneously permitting fluidto be exhausted through, the other port. This is a conventionalarrangement per se for causing reciprocation of a piston under ing alift frame simultaneously operated by a.

plurality of hydraulic jacks supporting the lift frame at differentpoints, it is very necessary and desirable to apply the same pressuresimultaneously to all of the jack pistons and to cause exactly the sametravel of all of said jack pistons. In order to accomplish this, it isnot only necessary to have the pump pistons of exactly the same size andthe jack pistons of exactly the same size, but to also have exactly thesame amount of power transmission fluid in each pump cylinder and thepassage placing the same in communication with a jack cylinder. In orderto do this by compensating for loss of any power transmission fluid fromany of the pump or jack cylinders, I provide the cylinder block 12 witha central chamber between the pump cylinders l4 and extending to aheight above the point where the lower ends of the pump pistons arelocated at their uppermost limits of travel, passages 26 being providedto afford communication at these points between the pump cylinders l4and chamber 25. Also, a liquid reservoir 21 is supported by the cylinderblock l2 at one side of the latter and has a bottom outlet 28communicating with one end of a passage 29 in the block l2 whose otherend communicates with the chamber 25. Reciprocable in the reservoir 21.is a plunger 30 yieldingly urged downwardly by a helical compressionspring 3| to force power transmission liquid from the reservoir 21 intothe pump cylinders when the passages 25 are opened upon the pump pistonsis reaching their upward limit of movement on each stroke thereof. Thus,the pump cylinders will be automatically kept filled with .powertransmission liquid,

a slight excess of liquid being forced back into the chamber 25 when thepump pistons it are forced downwardly, until they close the passages 26.In this way, exactly the sameamount of power transmission fluid isprovided for operatment and speed of travel of the lift frame by thelifting jacks 6.

From the foregoing description, it is believed that the construction andoperation, as well as the advantages, of the present invention will bereadily understood and appreciated by those skilled in the art.Obviously, while the invention is well adapted for use as a power liftfor molding machines, it will be evident that the same is capable ofgeneral application to any machine where it is desired to produce anabsolutely equal pressure in two or more lifting cylinders or two ingeach jack piston at all times, thereby insuring uniform application ofpressure to the jack pistons-and corresponding equal travel thereof.

The plunger 30 may be'guided by means of a stem 32 fixed thereto andslidable through a top closure 3: for the reservoir 21. Also, the baseplate 5 may have bleed passages I normally "closed by removable screwplugs 35, whereby air may be bled from the jack cylinders when the ormore cylinders oftwo or more lifting jacks. Minor changes in theadaptation and arrangement of parts, as well as in the details ofconstruction illustrated and described may therefore be made, such asfairly fall within the spirit and scope of the invention as claimed.

What I claim as new is:

l. A hydraulic lift comprising a plurality of spaced hydraulic liftingJacks having vertically movable pistons, a lift frame supported on saidpistons, a plurality of pumps arranged between and adapted for supplyingpower transmission fluid under pressure to said lifting jacks, therebeing one pump for each jack, and each pump including a verticallymovable piston, a single actuator for all of the pump pistons, and powermeans for moving said actuator, said actuator comprising a master pistonhaving the pump piston connected directly to the bottom face thereof,and a master cylinder for said master piston, and means for controllingthe admission of fluid under pressure to opposite ends of said mastercylinder.

2. A hydraulic lift comprising a plurality of spaced hydraulic liftingjacks having vertically movable pistons, a lift frame supported on saidpistons, a plurality of pumps for supplying power transmission fluidunder pressure to said lifting jacks, there being one pump for eachjack, and each pump including a vertically movable piston, a singleactuator for all of the pump pistons, and power means for moving saidactuator, and means for automatically filling thepump cylinders withpower transmission fluid upon completion of the retraction strokes ofsaid pump pistons, said last-named means comprising a reservoir forpower transmission fluid, a springactuated plunger for yieldinglyforcing the power transmission fluid from said reservoir, and passagesopening into the pump cylinders and constantly communicating with saidreservoir, said passages being located so as to be uncovered byapparatus is initially filled with power .transmission fluid. It will benoted that the apparatus involves a minimum number of movable parts thatare arranged so as to be effectively protected against foreign matterreadily failing the pump pistons when the latter approach their limit ofretracting movement.

3. A hydraulic lift comprising a base plate, a plurality of hydraulicjacks mounted on said base plate, one at each comer of the latter andeach including a vertically movable piston, a lift frame mounted uponthe pistons of said lifting jacks, a cylinder block mounted upon thebase plate intermediate the ends of the latter and having an uppermaster cylinder and a thereon, such as might cause undue wear of saidparts. Also, the construction is simple and compact, and it is such astoinsure efficient and reliable operation with a minimum amount of careor repair service. Obviously, the distance of travel of the masterpiston l1, as well as the speed of travel thereof, may be readilycontrolled through proper manipulation of the control valve I 24,thereby readily regulating the degree of moveplurality of lower pumpcylinders, pistons in said pump cylinders, there being one pump cylinderfor, each hydraulic Jack, passages in the base plate providingcommunication between each pump cylinder and one lifting Jack, a powerpiston connected to the pistons in the pump cylinders and operable inthe master cylinder, and means to control the admission of fluid underpressure to opposite ends of said master cylinder.

4. A hydraulic lift comprising a base plate. a

plurality of hydraulic Jacks mounted on said base 'a cylinder blockmounted form mounted on the plate, one at each corner of the latter andeach including a vertically movable piston, a lift frame mounted uponthe pistons of said lifting Jacks, upon the base plate intermediate theends of the latter and having an upper master cylinder and a pluralityof lower pump cylinders, there being one pump cylinder for eachhydraulic iack. passages in the base plate providing communicationbetween each pump cylinder and onelifting jack, a power 'piston operablein to control the admission of fluid under pressure to opposite ends ofsaid master cylinder, said lift frame comprising spaced parallel sideframe bars and U-shaped transverse members connecting said side framebars at points between the cylinder block and the lifting Jacks, and aplatcylinder block, said platform closing theupper end of der andsubstantially closing the space between the side frame bars.

5. A hydraulic lift comprising a base plate, a plurality of hydraulicjacks mounted on said base plate, one at each corner of the latter andthe master cylin-' 1 cylinders,

- each hydraulic Jack, passagesin the base plate the master cylinder,and means and operable in the master cylinder,

providing communication between each pump cylinder and one lifting lack,a power piston connected to the pistons in the pump cylinders and meansto control the admission of fluid under pressure uncovered by the pumppis to opposite ends" of said master cylinder, said cylinder blockhaving a central chamber and passages connecting the top of said chamberwith the pump cylinders directLv belowthe lower ends of the pump pistonswhen the latter are at their upward limit of movement, and means forautomatically maintaining said chamber fllled with power transmissionfluid and forcing the same into the pump cy ders when said passages areton. C. VICTOR HANSEN.

